The output of radio frequency (RF) receiver circuitry is temperature dependant. Conventionally, such RF receiver circuitry includes a thermistor coupled to the output signal line to compensate for temperature changes. A thermistor is a resistor which changes its value in response to changes in temperature. For land based radio equipment where the temperature changes are rarely dramatic, a thermistor-based temperature compensation circuit providing ±3 dB of compensation may be sufficient. However, avionic RF equipment, such as avionic Traffic Collision Avoidance System (TCAS) RF receivers and other avionic transponder RF receivers must meet governmental requirements, such as requirements by the United States' Federal Aviation Administration (FAA) for minimum trigger levels (i.e., the variation in a received signal which would trigger a response by the avionic RF equipment). While conventional avionic transponders control the minimum trigger level by providing a thermistor to change the log-video amplifier gain over temperature, current FAA guidelines have set a tighter requirement for the temperature dependency of the minimum trigger level than the ±3 dB that thermistor circuitry can provide.
Thus, it is desirable to provide a temperature compensation circuit for RF receiver circuitry that provides a tighter output variation over temperature than ±3 dB. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.